01-04 MPLS L2VPN Troubleshooting

VRP Troubleshooting - VPN Contents

Issue 01 (2008-08-20) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

i

Contents

4 MPLS L2VPN Troubleshooting ..............................................................................................4-1 4.1 MPLS L2VPN Overview ..............................................................................................................................4-2

4.1.1 Introduction to MPLS L2VPN.............................................................................................................4-2 4.1.2 CCC MPLS L2VPN.............................................................................................................................4-3 4.1.3 SVC MPLS L2VPN.............................................................................................................................4-4 4.1.4 Martini MPLS L2VPN.........................................................................................................................4-4 4.1.5 PWE3 MPLS L2VPN ..........................................................................................................................4-5 4.1.6 Kompella MPLS L2VPN.....................................................................................................................4-6 4.1.7 MPLS L2VPN IP-Interworking ...........................................................................................................4-6

4.2 L2VPN Troubleshooting ...............................................................................................................................4-7 4.2.1 Typical Networking..............................................................................................................................4-8 4.2.2 Configuration Notes...........................................................................................................................4-10 4.2.3 Troubleshooting Flowchart ................................................................................................................4-13 4.2.4 Troubleshooting Procedure ................................................................................................................4-14

4.3 Troubleshooting Cases ................................................................................................................................4-17 4.3.1 VC Type Is Found "Unsupport" When Setting Up a PW on an ATM Sub-interface..........................4-17 4.3.2 A Static PW Cannot Be Switched with Other PWs............................................................................4-19 4.3.3 Switch-L2VC Is Down After PW Switching Configuration ..............................................................4-21 4.3.4 PW Attributes Cannot Be Changed by Using the reset pw Command...............................................4-22 4.3.5 VC Is Up But the PPP Session Cannot Be Up ...................................................................................4-26 4.3.6 VC Under the Interface Is Missing After the Link Protocol Changes................................................4-27 4.3.7 Both the Session and the AC Are Up, But the VC Cannot Be Up......................................................4-29 4.3.8 Ethernet Interconnects with ATM, the VC Is Up, But the Ping Between CEs Fails ..........................4-33 4.3.9 CEs Cannot Communicate by Using the Accessing Mode of VLAN ................................................4-35 4.3.10 CEs Cannot Access Each Other Though the Static VC Is Up ..........................................................4-35 4.3.11 VC Is Down Though AC Is Up ........................................................................................................4-37 4.3.12 Large-Sized Packets Are Lost Between CEs on Two Ends of L2VPN ............................................4-38 4.3.13 Fail to Establish the MPLS LDP Session Between PEs When RIP-1 Are Used in the L2VPN Backbone....................................................................................................................................................................4-39

4.4 FAQs ...........................................................................................................................................................4-40 4.5 Diagnostic Tools..........................................................................................................................................4-44

4.5.1 display Commands.............................................................................................................................4-44 4.5.2 debugging Commands........................................................................................................................4-45

4 MPLS L2VPN Troubleshooting VRP

Troubleshooting - VPN

ii Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

Issue 01 (2008-08-20)

Figures

Figure 4-1 MPLS L2VPN networking ...............................................................................................................4-2

Figure 4-2 MPLS L2VPN label stack processing...............................................................................................4-3

Figure 4-3 Martini signaling process..................................................................................................................4-5

Figure 4-4 PWE3 signaling process ...................................................................................................................4-5

Figure 4-5 Local cross-connection networking ..................................................................................................4-8

Figure 4-6 Remote connection networking ........................................................................................................4-8

Figure 4-7 Multi-hop connection networking.....................................................................................................4-9

Figure 4-8 Inter-AS networking .......................................................................................................................4-10

Figure 4-9 Troubleshooting flowchart of the MPLS L2VPN remote connection fault ....................................4-13

Figure 4-10 Troubleshooting flowchart of the MPLS L2VPN local connection fault......................................4-14

Figure 4-11 Sketch map of the SVC remote connection label..........................................................................4-15

Figure 4-12 Sketch map of the CCC remote connection label .........................................................................4-16

Figure 4-13 Networking diagram of the switching between the static PW and dynamic PW..........................4-19

Figure 4-14 Networking diagram of Switch-L2VC troubleshooting................................................................4-21

Figure 4-15 Networking diagram .....................................................................................................................4-26



Figure 4-18 IP address configuration diagram .................................................................................................4-34

Figure 4-19 Networking diagram of the L2VPN backbone adopting RIP .......................................................4-39

Figure 4-20 Networking scheme using DCE and DTE as the interface types ..................................................4-41

VRP Troubleshooting - VPN 4 MPLS L2VPN Troubleshooting


4-1

4 MPLS L2VPN Troubleshooting

About This Chapter

The following table shows the contents of this chapter.

Section Description

4.1 MPLS L2VPN Overview This section describes the knowledge you need to know before troubleshooting MPLS L2VPN.

4.2 L2VPN Troubleshooting This section describes the notes about configuring MPLS L2VPN, and provides the MPLS L2VPN troubleshooting flowchart and the troubleshooting procedure in a typical MPLS L2VPN Network.

4.3 Troubleshooting Cases This section presents several troubleshooting cases.

4.4 FAQs This section lists frequently asked questions and their answers.

4.5 Diagnostic Tools This section describes common diagnostic tools: display commands and debugging commands.



4-2 Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

Issue 01 (2008-08-20)

4.1 MPLS L2VPN Overview This section covers the following topics:

Introduction to MPLS L2VPN CCC MPLS L2VPN SVC MPLS L2VPN Martini MPLS L2VPN PWE3 MPLS L2VPN Kompella MPLS L2VPN MPLS L2VPN IP-Interworking

4.1.1 Introduction to MPLS L2VPN

MPLS L2VPN MPLS L2VPN allows operators to provide Layer 2 VPNs of different media over a unified MPLS network. The MPLS network can also provide traditional IP, MPLS L3VPN, traffic engineering and QoS services.

From the users' point of view, the MPLS network is a Layer 2 switching network that can set up a Layer 2 connection between nodes.

Take ATM as an example. Every CE is equipped with an ATM VC, and connects the remote CE through the MPLS network.

Figure 4-1 MPLS L2VPN networking

CE

VC

VC VC

VC

CE

CECE

VPN A

VPN B

VPN A

VPN B

PEPE

PE

P

LSP

Basic Concepts of MPLS L2VPN The CE, PE and P defined in the MPLS L2VPN have the same meaning and mechanism as those in the BGP/MPLS L3VPN.



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The MPLS L2VPN also uses a label stack to implement transparent transmission of packets across the MPLS network.

The outer label, called the tunnel label, is used to transport packets from one PE to another PE.

The inner label, called the VC label, is used to distinguish connections in different VPNs. According to the VC label, the receiving PE determines the CE where the packet is forwarded.

Figure 4-2 shows the change of label stack in the process of forwarding packets across the MPLS L2VPN.

Figure 4-2 MPLS L2VPN label stack processing

PCE 1 CE 2PE 1 PE 2

L2PDU L2PDUL2PDUT' VL2PDUT V

Here, L2PDU represents the link layer packet; T represents the tunnel label; V represents the VC label; and, T' represents a modified outer label.

Implementation of MPLS L2VPN The Provider-Provisioned Virtual Private Network (PPVPN) workshop of the IETF draws up multiple MPLS L2VPN framework drafts. Martini and Kompella are the major drafts.

draft-martini-l2circuit-trans-mpls: uses LDP as the signaling protocol to transfer Layer 2 information and VC labels.

draft-kompella-ppvpn-l2vpn: uses BGP as the signaling protocol to transport Layer 2 information and VC labels.

You can also use static VC label configuration, such as CCC and SVC to implement MPLS L2VPN.

The process of implementation is described as follows.

4.1.2 CCC MPLS L2VPN Circuit Cross Connect (CCC) implements MPLS L2VPN by means of static configuration.

Unlike common MPLS L2VPNs, CCC uses a one-level label to transport user data and it occupies a static LSP exclusively.

There are two types of CCC connection.

Local connection: refers to the connection between two local CEs. The two CEs are connected to the same PE. Here, the PE functions as a Layer 2 switch that can carry out switching without a static LSP.

Remote connection: refers to the connection between a local CE and a remote CE. The two CEs are connected to different PEs, and a static LSP is required to transmit packets from one PE to another PE. Static LSPs and CCC connections can be associated by using a CLI command on the PE.




Issue 01 (2008-08-20)

4.1.3 SVC MPLS L2VPN SVC is another type of static MPLS L2VPN. The SVC transfers L2VPN information without using the signaling protocol. But it requires manual configuration of VC label information.

When creating a static SVC L2VPN connection, you can use a tunnel policy to specify the tunnel type, which can be an LDP LSP, CR LDP or GRE tunnel. Load balancing is also supported.

The SVC supports multi-hop inter-AS L2VPN but does not support local connection.

CCC, SVC and static LSP use the same label range of 16 to 1023.

4.1.4 Martini MPLS L2VPN Martini mode is simple. It implements L2VPN by setting up a point-to-point link and transports Layer 2 information and VC labels using LDP.

In Martini mode, you can identify a VC between two CEs by using the VC type together with the VC ID.

VC type: represents the encapsulation type of a VC, which can be ATM (atm-aal5-sdu), VLAN or PPP.

VC ID: is used to flag a VC. For VCs of the same type, their VC ID must be unique on the same PE.

PEs exchange VC labels using LDP and associate CEs using the VC ID. After a tunnel is set up successfully between PEs and label exchange, and bindings are completed, a VC is established.

For the remote connection, you need to establish a remote LDP session to transport VC FECs and VC labels. This is because, the two PEs that exchange VC labels may not be directly connected.

The Martini mode supports multi-hop inter-AS L2VPN but does not support local connection.

Martini MPLS L2VPN supports Graceful Restart (GR) . After router switchover the VC label remains unchanged. During the switchover, the VC remains Up.

After the switchover, the original label saved at the local end will be deleted if found different from the one learned from the LDP peer. The VC that uses this label then becomes Down.

Figure 4-3 shows the Martini signaling process.



4-5

Figure 4-3 Martini signaling process

Mapping

Mapping

Withdraw

Release

Create PW Create PW

AC/TNLDown

4.1.5 PWE3 MPLS L2VPN Pseudo-Wire Emulation Edge-to-Edge (PWE3) is an extension of Martini mode.

The PWE3 sets up a PW on the control plane by using LDP. On the basis of the Martini mode, PWE3 adds a Notification mechanism and reduces the interaction of control packets when the AC or the tunnel flaps. The PWE3 can also use L2TPv3 as the signaling. The RSVP can be used as a signaling protocol to set up a PW with bandwidth guarantee, that is, RSVP-TE PW. PWE3 mode is compatible with Martini mode.

Figure 4-4 shows the PWE3 signaling process.

Figure 4-4 PWE3 signaling process

Mapping

Mapping

Withdraw

Release

Delete PW

Create PW

AC/TNL

Create PW

Notification




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4.1.6 Kompella MPLS L2VPN

Overview Kompella mode implements L2VPN in an end-to-end fashion and uses BGP to transport Layer 2 information and VC labels.

Unlike Martini mode, Kompella MPLS L2VPN requires dividing the entire operator network into many VPNs, and globally numbering CEs within these VPNs instead of processing the connection between CEs directly.

Similar to BGP/MPLS VPN, Kompella mode also uses the VPN target to control the sending and receiving of VPN routes. This adds more flexibility to networking.

To set up a connection between two CEs, you need to specify a separate CE ID for both the local CE and the remote CE on the PE.

The Kompella mode supports local connection and remote connection. Kompella mode supports the following two types of inter-AS L2VPN.

Multi-Hop mode: adopts BGP label routes. MP-EBGP mode: stores the label block on the ASBR.

Label block In Kompella mode a label block is used to distribute labels. Labels can be allocated for multiple connections at a time.

Users can specify a local CE range that shows the number of CEs a local CE can connect. The system allocates one label block to this local CE at a time, with the block size equal to the CE range. This mode allows users to distribute extra labels for VPNs. This causes a waste of labels in a short term but reduces the workload of future VPN expansion.

4.1.7 MPLS L2VPN IP-Interworking Two CEs of the same L2VPN may use different Layer 2 media to access the SP. To allow them to communicate, you must configure L2VPN IP-interworking.

Configuration notes vary with the Layer 2 medium through which the CE connects to the SP.

PE mentioned in the following section refers to a local PE unless otherwise stated.

Ethernet and VLAN An interface or sub-interface of any Ethernet type supports IP-interworking encapsulation. Note the following points:

It is not required to assign an IP address for the Ethernet interface on PE. Even if an IP address is assigned, no routes can be generated.

After the encapsulation, the Ethernet interface of PE processes only ARP packets and IP packets. Other types of packets are discarded.

After receiving IP packets from CE, PE will not update dynamic MAC addresses. If you configure IP-interworking encapsulation on an ATM interface or sub-interface, you

cannot configure this encapsulation on the VE interface that is associated with the PVC.



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The minimum VLAN IDs of the neighboring PE and CE must be the same; while that of the CEs on two ends of the tunnel can be different.

The processing of ARP packets:

After IP-interworking encapsulation, the Ethernet interface will have ARP entries that are different from ordinary entries.

On receiving an ARP request from CE, the IP interworking-encapsulated L2VPN incoming interface of PE will respond with its own MAC address regardless of the destination.

An Ethernet interface or sub-interface of PE can connect only one CE, it cannot connect multiple CEs by using a Hub or LAN switch. Otherwise, PE may learn useless MAC addresses, leading to forwarding failure.

PPP PPP supports PAP and CHAP authentication. PPP supports local, RADIUS and

HWTACACS authentication. PPP supports STAC-LZS compression other than IPHC and VJ compression. PE can assign IP addresses for CEs; CE can also assign IP addresses for PEs. The

mechanism of address allocation is similar to the common case. PPP supports transparent transmission of IP packets rather than MPLS, IS-IS, and IPX

packets from a local CE to a remote CE. If any of these protocols is configured on the interface, NCP will still be negotiated but the protocol packet will not be forwarded.

For PPP links, it is recommended to select the way of CE allocating IP addresses to PE. This can avoid address conflict on PE and facilitate network deployment.

Frame Relay Supports FRF.9 compression but does not support compression of the IP header in the FR

frame. Supports the Local Management Interface (LMI) protocol. Supports the Inverse Address Resolution Protocol (INARP). Supports transparent transmission of IP packets from a local CE to a remote CE, but does

not support that of MPLS packets, IS-IS packets, and IPX packets.

When configuring FR, note the following points:

You must specify a VC number for an interface of DCE or NNI type, whether it is a main interface or a sub-interface.

For an interface of DTE type, if it is a main interface, the system can automatically determine the VC number based on the remote device; if it is a sub-interface, you must manually specify a VC number for it.

4.2 L2VPN Troubleshooting This section covers the following topics:

Typical Networking Configuration Notes




Issue 01 (2008-08-20)

Troubleshooting Flowchart Troubleshooting Procedure

4.2.1 Typical Networking

Local Cross-Connection Networking

Figure 4-5 Local cross-connection networking

CE 1

CE 2

PE

POS 1/0/0100.1.1.1/24

POS1/0/0100.1.1.2/24

POS 1/0/0POS 2/0/0

local connection

Only the CCC mode and the Kompella mode support local cross-connection. Both the modes support IP-interworking in the case of local cross-connection.

The label does not change during data forwarding on PE.

Remote Connection Networking

Figure 4-6 Remote connection networking

POS 2/0/0168.1.1.1/24

POS 1/0/0168.1.1.2/24

POS 2/0/0169.1.1.1/24

POS 1/0/0169.1.1.2/24

POS 1/0/030.1.1.1/24

P PE 2PE 1

CE 1 CE 2

POS 2/0/0POS 1/0/0

POS 1/0/030.1.1.1/24

Loopback11.1.1.9/32

Loopback12.2.2.9/32

Loopback13.3.3.9/32

Remote Connection

The networking shown in Figure 4-6 is applicable for all L2VPN remote connections.



4-9

Multi-hop Connection Networking

Figure 4-7 Multi-hop connection networking

CE-A CE-B

U-PE1

Multi-Hop-PW

U-PE2

S-PE

Loopback03.3.3.9/32

Loopback02.2.2.9/32 4.4.4.9/32

Loopback01.1.1.9/32

Loopback05.5.5.9/32

P1 P2

Loopback0

The networking shown in Figure 4-7 is applicable for multi-hop PWE3, including LDP-PW, and static-PW.

A PW is configured on the interface of U-PE. The PW switching is configured in the system view on S-PE.




Issue 01 (2008-08-20)

Inter-AS Networking

Figure 4-8 Inter-AS networking

PE2

ASBR-PE2

AS 200

ASBR -PE1

PE1

AS 100

GE2/0/010.1.1.2/24

Loopback11.1.1.9/32

POS2/0/0192.1.1.1/24

Loopback12.2.2.9/32

Loopback13.3.3.9/32

Loopback14.4.4.9/32

GE2/0/010.2.1.2/24

CE1 AS 65001 CE2AS 65002

GE1/0/010.1.1.1/24

GE1/0/010.2.1.1/24

POS2/0/0192.1.1.2/24

Kompella supports three inter-AS implementations namely, VRF-to-VRF, multi-hop, and MP-EBGP. Martini and SVC support the inter-AS both in the VRF-to-VRF mode and the Multi-Hop mode.

4.2.2 Configuration Notes

Item Sub-item Notes

Configuring LSR-ID

An LSR ID is similar to the Router ID. An LSR ID actually specifies an address. By default, LDP uses this address to establish an LDP session, so ensure the accessibility of the route to it. There are two methods of setting an LSR ID.

Ensure that the LSR-ID is unique in the backbone network. The LSR ID is generally set to the address of the loopback interface.

If the mpls ldp transport-address command is configured on the interface connecting the public network, LDP will use the address specified by this command to establish an LDP session.

Configuring MPLS

Configuring MPLS

You need to enable MPLS in the system view



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Item Sub-item Notes

Establishing the MPLS LDP session (dynamic VC connection)

Configuring MPLS LDP or remote MPLS LDP

The dynamic VC connection uses the LDP as the signaling. If PEs are not connected directly, the remote MPLS LDP session must be set up between PEs.

Configuring AS

You should specify the same AS for all related PEs and Ps.

Configuring interface used for BGP connection

You need to specify the loopback interface (with a 32-bit mask) as the egress interface of the session that is used to establish an IBGP connection between PEs.

Configuring BGP (remote connection using BGP as the signaling)

Enabling a specified peer

In the L2VPN address family view, you need to specify a peer or peer group between which the routing information is exchanged.

Enabling MPLS L2VPN

Configuring MPLS L2VPN

Whatever MPLS L2VPN mode you choose, you must enable MPLS L2VPN globally.

Configuring the Attached Circuit (AC)

Configuring Encapsulation type, MTU and interface parameters of the specific link type

The L2VPN can be in the Up state only when the status of AC is Up.

If the AC type is VLAN, the sub-interface can be either the one based on the Ethernet or the VLANIF interface based on the port.

If the AC type is ATM, configure the VC.

Creating a connection

For the SVC mode, create the static L2VC in the interface view.

For the Martini mode, create the L2VC in the interface view.

For the CCC mode, create the CCC connection in the system view.

For the Kompella mode, create the CE connection.

Specifying an encapsulation type for the interface

For an L2VC connection the encapsulation type must be consistent on the interface at both VC ends.

Configuring a connection

Configuring the VC ID

The VC IDs of the SVC on S-PE can be the same. However, the VC ID of the same encapsulation type on U-PE must be unique. Change the encapsulation type on U-PE may lead to the collision of the VC ID. For the static PW, the default VC ID is 0. If the static PW is used in the switching, a non-zero VC ID needs to be configured.




Issue 01 (2008-08-20)

Item Sub-item Notes

Specifying the MTU size for the interface

For an LDP VC, the MTU is one of key parameters to be negotiated. The MTU size must be the same on both ends of a VC; otherwise, the VC will not go Up. For U-PE, the MTU is specified in the interface view. For S-PE, the MTU is specified when switching VCs is configured.

Configuring switching VC

For the multi-hop PW, you need to configure switching VCs.

Configuring receiving and sending labels

For the static remote connection, the receiving and sending label need to be configured manually.

The configuration changes with MPLS L2VPN implementation mode. For details of the configuration, refer to the VRP Configuration Guide - VPN.



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4.2.3 Troubleshooting Flowchart

Remote Connection

Figure 4-9 Troubleshooting flowchart of the MPLS L2VPN remote connection fault

Yes

Yes

Yes

Yes

Yes

No

No

No

No

YesNo

No

Yes

Yes

Yes

Yes

No

No

No

End

No

EndYes

No

No

Yes

CEs cannotaccess

each other

AC is Up?CEs can

access eachother?

L2VPNconnection is

Up?

Tunnelbetween PEs

is Up?

Ensure thetunnel is Up

L2VPNconnection is

Up?

BGP/LDPsession is set

up?

Set upBGP/LDPsession

between PEs

L2VPNconnection is

Up?

L2VPNconnection is

Up?

CEs canaccess each

other?

Ensure ACinterfaces of CE

on same segment

Ensureparametersconsistent

Parametersare consistent?

Seektechnicalsupport

Heteromediainterconnect?

Remove AC link

negotiationfault

ReconfigureVC or seektechnicalsupport

Ensure thatAC is Up

CEs canaccess each

other?




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Local Connection

Figure 4-10 Troubleshooting flowchart of the MPLS L2VPN local connection fault

Yes

Yes

No

Yes

NoNo

Yes

End

No

Yes

No

Yes

No

Yes

No

CEs cannotaccess each

other

AC is Up? Ensure ACis Up

L2VPNconnection

is Up?

CEs canaccess each

other?

Ensure ACinterfaces of CE

on samesegment

Encapsu-lation

is correct?

Re-configurethe type

CEs canaccess each

other?

Heteromediainterconnect?

Remove AC linknegotiation fault

Reconfigureconnection orseek technical

support

CEs canaccess each

other?

4.2.4 Troubleshooting Procedure The steps of troubleshooting are as follows:

Step 1 Check the AC status of the PE of both ends.

Before setting up the L2VPN connection, ensure the AC status is Up. If the status of AC is Down, remove the fault on the AC link and ensure the AC status on PE is Up.

When the AC type is VLAN, the sub-interface needs to be configured. When the AC type is ATM, the VC needs to be configured.

Step 2 Check the status of the L2VPN connection.

Use the following command in any view on PE to check the AC status and the L2VPN connection status.



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In CCC mode, use the display ccc command or the display l2vpn ccc-interface vc-type command.

In SVC mode, use the display mpls static-l2vc command. In Martini mode, use the display mpls l2vc command. In Kompella mode, use the display mpls l2vpn connection command.

If the status of the connection is Up, but the packet cannot be forwarded normally, check that the AC interfaces on CE are on the same network segment.

For the static VC, check that the in-label and the out-label, and that of the remote end are consistent.

transmit-vpn-label on the local end and receive-vpn-label on the remote end are consistent.

receive-vpn-label on the local end and transmit-vpn-label on the remote end are consistent.

If still the CEs cannot communicate, use the display fib command and the display ip routing-table command to view whether the forwarding table and the routing table are consistent.

If they are not consistent, the forwarding entry may not be delivered. You need to delete the VC and re-configure it.

If they are consistent, contact the Huawei technical personnel.

If the status of the L2VPN is Down, do as follows.

Step 3 Do as follows in the case of remote connection.

1. Check that the outer tunnel (public network tunnel) exists. L2VC connection: Run the display mpls l2vc interface command. If "VC tunnel/token

info" is missing in the output, check if the tunnel configuration is correct. If it is existing, but "TNL ID" is "0x0", check that routes are reachable to both ends of a tunnel. If it is an SVC connection, check if the label at both ends match. For a same SVC connection, the egress label of one end must be the ingress label of another end as shown in Figure 4-11.

Figure 4-11 Sketch map of the SVC remote connection label

O-Label

200

I-Label

200

I-Label

100

O-Label

100

PE 1 to PE 2

PE 2 to PE 1

PE 1 PE 2

Kompella mode: Run the display mpls l2vpn connection interface command. If "tunnel type" is missing in the output, or "id" that follows is 0x0, check that the routes are reachable at both ends of a tunnel.

Remote CCC connection: Run the display ccc command to check that the label at both ends match. For a same CCC connection, the egress label of one end must be the ingress label of another end as shown in Figure 4-12.




Issue 01 (2008-08-20)

Figure 4-12 Sketch map of the CCC remote connection label

O-Label

200

I-Label

200

O-Label

201

I-Label

201

I-Label

100

O-Label

100

I-Label

101

O-Label

101

CE 1 to CE 2

CE 2 to CE 1

2. Check that the BGP connection or the MPLS LDP session is established successfully. If LDP is used as the signaling protocol, use the display mpls ldp session command to

check the establishment of a session. If PEs are connected indirectly, the MPLS LDP remote session needs to be set up between PEs.

If BGP is used as the signaling protocol, use the display bgp vpnv4 vpn-instance vpn-instance-nam all peer command to check that the BGP session is set up successfully.

For the diagnosis of MPLS LDP session faults, refer to Chapter 3 "MPLS LDP Troubleshooting."

For the BGP troubleshooting, refer to the VRP Troubleshooting - IP Routing.

If the BGP connection or the MPLS LDP session is set up successfully, but still the L2VPN cannot be set up, perform the following checks.

3. Check that negotiated parameters match.

Parameter mismatch may appear in various forms, as in the following examples:

The MTU of one end is 1500 bytes, but that of the other end is 4470 bytes. One end supports CW while the other end does not. One end is encapsulated with PPP while the other end is encapsulated with Ethernet.

If the negotiated parameters mismatch, modify them to be consistent.

In the case of the heterogeneous-media interconnection, the encapsulation type of the connection should be IP-interworking.

If the status of VC is Down even after the configuration, do as follows.

Step 4 Do as follows in the case of the local connection.

Check that the encapsulation types are consistent on both local and remote ends if the local connection is Down.

Step 5 Check whether the link negotiation between CE and PE succeeds when heterogeneous media are interconnected.

If the negotiated parameters of the link between CE and PE mismatch, modify them to be consistent.

In the case of the Ethernet network, check that local ce-mac or local ce-ip is configured.

If the fault is still not rectified, check that the local PE is configured with the IP address of the remote CE.

If the fault persists, contact Huawei technical personnel.

----End



4-17

4.3 Troubleshooting Cases This section provides the following troubleshooting cases:

VC Type Is Found "Unsupport" When Setting Up a PW on an ATM Sub-interface A Static PW Cannot Be Switched with Other PWs Switch-L2VC Is Down After PW Switching Configuration PW Attributes Cannot Be Changed by Using the reset pw Command VC Is Up But the PPP Session Cannot Be Up VC Under the Interface Is Missing After the Link Protocol Changes Both the Session and the AC Are Up, But the VC Cannot Be Up Ethernet Interconnects with ATM, the VC Is Up, But the Ping Between CEs Fails CEs Cannot Communicate by Using the Accessing Mode of VLAN CEs Cannot Access Each Other Though the Static VC Is Up VC Is Down Though AC Is Up Large-Sized Packets Are Lost Between CEs on Two Ends of L2VPN Fail to Establish the MPLS LDP Session Between PEs When RIP-1 Are Used in the

L2VPN Backbone

4.3.1 VC Type Is Found "Unsupport" When Setting Up a PW on an ATM Sub-interface

Fault Symptom Configuration of PWE3 is required. After a PW is established on the ATM sub-interface of U-PE, use the display mpls l2vc command to check it. However, "VC Type" is found to be "Unsupport". For example:

[Quidway] interface atm 2/1/0.100 [Quidway-Atm2/1/0.100] mpls l2vc 3.3.3.8 33 [Quidway-Atm2/1/0.100] display mpls l2vc interface atm 2/1/0.100 *Client Interface : Atm2/1/0.100 is up Session State : down AC State : down VC State : down VC ID : 33

VC Type : Unsupport Destination : 3.3.3.8

Local Group ID : 0

Remote Group ID : 0

Local VC Label : 119809

Remote VC Label : 0

Local VC MTU : 1500

Remote VC MTU : 0

Local VCCV : Disable Remote VCCV : None Local Frag : Disable Remote Frag : None Local Ctrl Word : Disable Remote Ctrl Word : None




Issue 01 (2008-08-20)

Tunnel Policy : --

Traffic Behavior : --

PW Template Name : --

VC tunnel/token info : 0 tunnels/tokens Create time : 0 days, 0 hours, 0 minutes, 9 seconds UP time : 0 days, 0 hours, 0 minutes, 0 seconds Last change time : 0 days, 0 hours, 0 minutes, 9 seconds

Fault Analysis By default, an ATM sub-interface uses the Point-to-Multipoint Protocol (P2MP) as the link layer protocol. However, PWE3 does not support P2MP.

So, you must specify Point-to-Point (P2P) for it when creating an ATM sub-interface.

After specifying P2P, you need to reconfigure the PW. The configuration is as follows.

[Quidway] interface atm 2/1/0.100 p2p [Quidway-Atm2/1/0.100] mpls l2vc 3.3.3.8 33

Check the output and you can find that "VC Type" becomes "atm aal5 sdu".

[Quidway-Atm2/1/0.100] display mpls l2vc interface atm 2/1/0.100 *Client Interface : Atm2/1/0.100 is up Session State : down AC State : up VC State : down VC ID : 33

VC Type : atm aal5 sdu Destination : 3.3.3.8

Local Group ID : 0

Remote Group ID : 0


Remote VC Label : 0

Local VC MTU : 1500

Remote VC MTU : 0

Local VCCV : Disable Remote VCCV : None Local Frag : Disable Remote Frag : None Local Ctrl Word : Enable Remote Ctrl Word : None Tunnel Policy : --




Troubleshooting Procedure Step 1 Specify P2P as the link layer protocol of an ATM sub-interface.

Step 2 Reconfigure the PW.

----End



4-19

Summary While configuring PWE3, you must specify P2P as the link layer protocol for the sub-interface to create a PW on an ATM sub-interface.

4.3.2 A Static PW Cannot Be Switched with Other PWs

Fault Symptom After configuring static PW, find that the static PW cannot be switched with other PWs as shown in Figure 4-13.

Figure 4-13 Networking diagram of the switching between the static PW and dynamic PW

U-PE2

CE-A CE-B

Loopback01.1.1.9/32

POS2/0/020.1.1.1/24

POS1/0/020.1.1.2/24

POS1/0/010.1.1.2/24

POS2/0/010.1.1.1/24

POS1/0/0100.1.1.1/24

POS1/0/0 POS2/0/0

POS1/0/0100.1.1.2/24

Dynamic PW

Loopback02.2.2.9/32

Loopback03.3.3.9/32

U-PE1 S-PE

MPLS Backbone

Static PW

PW Switching

For example:

# Configure a static PW on U-PE1.

[U-PE1-Pos1/0/0] mpls static-l2vc destination 3.3.3.3 transmit-vpn-label 100

receive-vpn-label 100

# Configure a static PW on U-PE2.

[U-PE2-Pos1/0/0] mpls static-l2vc destination 1.1.1.1 transmit-vpn-label 100


# Configure static PW switching on S-PE.

[S-PE] mpls switch-l2vc 3.3.3.3 100 trans 100 recv 100 between 1.1.1.1 100 trans 100

recv 100 encapsulation ppp

Fault Analysis The VC ID is optional for the static PWE3. The static PW without a VC ID cannot be switched with the dynamic PW.




Issue 01 (2008-08-20)

When configuring the mixed PW switching, you can specify a non-zero VC ID for the static PW. Otherwise, the multi-hop PW (MH-PW) cannot be located. Normally, the VC ID for the static PW is the same as that of the dynamic PW.

In this case, the possible cause is that the PW ID of the static PW is 0. You can use the following method to solve it.

# Configure U-PE1.

[U-PE1] pw-template pwt1 [U-PE1] peer-address 3.3.3.3 [U-PE1-Pos1/0/0] mpls static-l2vc pw-template pwt1 1 transmit-vpn-label 100


# Configure U-PE2.

[U-PE1] pw-template pwt1 [U-PE1] peer-address 1.1.1.1 [U-PE1-Pos1/0/0] mpls static-l2vc pw-template pwt1 1 transmit-vpn-label 100


# Configure static PW switching on S-PE.

[S-PE] mpls switch-l2vc 3.3.3.3 100 trans 100 recv 100 between 1.1.1.1 100 trans 100

recv 100 encapsulation ppp

Establishment of the static PW does not involve the signaling. As long as the label is correct, VC IDs can be different.

Troubleshooting Procedure Step 1 Create a PW template in the system view.

Step 2 Specify a peer for the PW in the PW template.

Step 3 Create a PW by using the PW template and specify a non-zero PW ID (also called VC ID) for it. Or specify a non-zero VC ID for the static PW.

----End

Summary The PW ID for the static PW is optional as required.

Static PWs to be switched must be configured with a PW ID.



4-21

4.3.3 Switch-L2VC Is Down After PW Switching Configuration

Fault Symptom

Figure 4-14 Networking diagram of Switch-L2VC troubleshooting

U-PE2

CE-A CE-B

Loopback01.1.1.9/32

POS2/0/020.1.1.1/24

POS1/0/020.1.1.2/24

POS1/0/010.1.1.2/24

POS2/0/010.1.1.1/24

POS1/0/0100.1.1.1/24

POS1/0/0 POS2/0/0

POS1/0/0100.1.1.2/24

PW

Loopback02.2.2.9/32

Loopback03.3.3.9/32

U-PE1 S-PE

MPLS Backbone

PW

PW Switching

The configuration is as follows.

# Configure S-PE.

[S-PE] mpls switch-l2vc 1.1.1.9 45 between 2.2.2.9 34 encapsulation vlan

# Display the configuration and find that the status of the switch-L2VC is Down.

[S-PE] display mpls switch-l2vc *Switch-l2vc type : LDP<---->LDP Peer IP Address : 2.2.2.9, 1.1.1.9 VC ID : 45, 34

VC Type : vlan VC State : down Local/Remote Label : 119812/0, 119813/0

Local/Remote Control Word : Disable/None, Disable/None Local/Remote VCCV Capality : Disable/None, Disable/None Local/Remote Frag Capability : Disable/None, Disable/None Switch-l2vc tunnel info : 0 tunnels for peer 2.2.2.9 1 tunnels for peer 1.1.1.9 NO.0 TNL Type : lsp , TNL ID : 0x8b010000 Create time : 0 days, 0 hours, 0 minutes, 9 seconds UP time : 0 days, 0 hours, 0 minutes, 0 seconds Last change time : 0 days, 0 hours, 0 minutes, 9 seconds




Issue 01 (2008-08-20)

Fault Analysis The VRP does not necessarily require a VC peer to use the remote MPLS LSR ID. When using the MPLS LDP, you must use the LSR-ID specified in the MPLS LDP view as the LSR-ID. Therefore, the VC peer can be the remote MPLS LSR ID, or the 32-bit mask address of a loopback interface. The session between the two ends can be established by using the remote peer command.

An LSR cannot establish a session or LSP with itself. If a VC between an LSR and its remote is configured on S-PE where PW switching is done, then, this VC cannot be Up. The remote address used for PW switching cannot be the address of the local router.

Troubleshooting Procedure Step 1 Check the peer IP address of the VC on S-PE.

Step 2 Modify the peer IP address used in the PW switching to the non-local S-PE router address.

----End

Summary When configuring a multi-hop PW, note that a VC cannot be set up between S-PE and U-PE.

4.3.4 PW Attributes Cannot Be Changed by Using the reset pw Command

Fault Symptom After PW configuration on PE, users change PW attributes.

Use the reset pw template command and the reset pw vc-id command. Find that PW attributes are unchanged.

# Check the configuration of the PW template on PE.

[PE] display pw-template pwt1 PW Template Name : pwt1 PeerIP : 1.1.1.1

Tnl Policy Name : --

PW Type : Unknown CtrlWord : Disable MTU : 1500

MaxAtmCells : 1

VCCV Capability : Disable Fragmentation : Disable Behavior Name : --

Total PW : 1, Static PW : 1, LDP PW : 0

# Configure a PW by applying the PW template.

[PE-Atm2/1/0.100] mpls l2vc pw-template pwt1 2.2.2.2 100

# View the PW configuration.

[PE-Atm2/1/0.100] display mpls l2vc 100 Total ldp vc : 1 0 up 1 down



4-23

*Client Interface : Atm2/1/0.100 Session State : down AC Status : up VC State : down VC ID : 100 VC Type : atm aal5 sdu Destination : 2.2.2.2


Remote VC Label : 0

Control Word : Disable Local VC MTU : 1500

Remote VC MTU : 0

Tunnel Policy Name : --

Traffic Behavior Name: --

PW Template Name : pwt1 Create time : 0 days, 0 hours, 0 minutes, 6 seconds UP time : 0 days, 0 hours, 0 minutes, 0 seconds Last change time : 0 days, 0 hours, 0 minutes, 6 seconds

# Specify a new peer address for the PW in the PW template.

[PE-Atm2/1/0.100] pw-template pwt1 [PE-pw-template-pwt1] peer-address 3.3.3.3 Info: The attribute of this PW template has been modified, please use PW restart command

to update PW's attribute

According to the prompt, do as follows.

[PE-pw-template-pwt1] return

# Reset the PW.

<PE> reset pw 100 atm-aal5-sdu

# Display the configuration and find that the peer IP address of the PW is unchanged.

<PE> display mpls l2vc 100 Total ldp vc : 1 0 up 1 down *Client Interface : Atm2/1/0.100 Session State : down AC Status : up VC State : down VC ID : 1



Remote VC Label : 0


Remote VC MTU : 0







Issue 01 (2008-08-20)

# Reset the PW template.

<PE> reset pw pw-template pwt1

# Display the configuration and find that the peer IP address of the PW does not change.

<PE> display mpls l2vc 100 Total ldp vc : 1 0 up 1 down *Client Interface : Atm2/1/0.100 Session State : down AC Status : up VC State : down VC ID : 1



Remote VC Label : 0


Remote VC MTU : 0




Fault Analysis Some PW attributes can be configured by using the PW template or by using the CLI command. However, the latter method has the highest priority.

If PW attributes are specified in the CLI, then those specified in the PW template lose effect. The PW attributes will not change if the reset pw template and the reset pw vc-id commands are run.

In this case, you can use the PW template to set PW attributes that need changes. To set this, perform the following actions:

# Specify the peer IP address in the PW template.

[PE-Atm2/1/0.100] pw-template pwt1 [PE-pw-template-pwt1] peer-address 3.3.3.3

# Apply the template to the PW.

[PE-pw-template-pwt1] int atm 2/1/0.100 [PE-Atm2/1/0.100] mpls l2vc pw-template pwt1 100

# Display the configuration and find that the IP address of the PW peer is unchanged.

[PE-Atm2/1/0.100] display mpls l2vc 100 Total ldp vc : 1 0 up 1 down *Client Interface : Atm2/1/0.100 Session State : down AC Status : up VC State : down VC ID : 100



4-25

VC Type : atm aal5 sdu Destination : 2.2.2.2 Local VC Label : 119811

Remote VC Label : 0


Remote VC MTU : 0



PW Template Name : pwt1 Create time : 0 days, 0 hours, 0 minutes, 4 seconds UP time : 0 days, 0 hours, 0 minutes, 0 seconds Last change time : 0 days, 0 hours, 0 minutes, 4 seconds [PE-Atm2/1/0.100] return <PE> reset pw 100 atm-aal5-sdu

# Display the configuration and find that the IP address of the PW peer changes.

<PE> display mpls l2vc 100 Total ldp vc : 1 0 up 1 down *Client Interface : Atm2/1/0.100 Session State : down AC Status : up VC State : down VC ID : 100 VC Type : atm aal5 sdu Destination : 3.3.3.3


Remote VC Label : 0


Remote VC MTU : 0




Troubleshooting Procedure Step 1 Create a PW template and set PW attributes (especially those needing changes) on it.

Step 2 Apply the PW template to the PW.

Step 3 Run the reset pw template command or the reset pw vc-id command in the user view to modify PW attributes.

----End

Summary The reset pw template command or the reset pw vc-id command can only change the attributes that are set by using the PW template.




Issue 01 (2008-08-20)

4.3.5 VC Is Up But the PPP Session Cannot Be Up

Fault Symptom

Figure 4-15 Networking diagram

CE1 CE2

PE1 PE2

POS1/0/0

POS1/0/0 POS1/0/0

POS1/0/0

GE2/0/0

GE2/0/0

The CE and PE are connected through a POS interface. The PE and PE are connected through a GE interface.

The VC is Up, but the PPP session cannot be Up. If a POS interface is used to connect PEs, the PPP session between CE and PE goes Up.

Fault Analysis That the VC on PE is Up is because there is a tunnel between PEs and the CE-bound PE interface is Up administratively.

To enable a PPP session to be Up, PPP negotiation must succeed.

The PPP negotiation is carried out between two CE interfaces. The PE connects the public network through an Ethernet-type interface whose minimum packet is defined to be 64 bytes long. The PPP control packet, LCP packet, is very small and is less than 64 bytes even after two layers of labels are added. Consequently, the GE interface on PE discards this negotiation packet. This will cause the failure in transmitting the negotiation packet to the remote CE over the VC.

Troubleshooting Procedure Step 1 Connect PEs by using the POS interface. Alternatively, run the mpls l2vc peer-ip-address

[ vc-id ] control-word command on the two PEs to configure a control word for L2VPN. Padding will be automatically added to L2VPN packets.

----End

Summary When the type of the link between CE and PE is different from that between PEs, check the minimum MTU value.



4-27

4.3.6 VC Under the Interface Is Missing After the Link Protocol Changes

Fault Symptom The configuration is as follows.

# Configure MPLS L2VC on an interface on PE that connects the AC. Set the VC ID to 100.

[PE-Pos4/0/0] mpls l2vc 1.1.1.8 100

# View the configuration of the interface.

[PE-Pos4/0/0] display this #

interface Pos4/0/0 link-protocol fr mpls l2vc 1.1.1.8 100 #

return

# This interface has a VC with the VC ID of 100.

[PE-Pos4/0/0] display mpls l2vc interface pos 4/0/0 *Client Interface : Pos4/0/0 is down Session State : down AC State : down VC State : down VC ID : 100 VC Type : fr Destination : 1.1.1.8

Local Group ID : 0

Remote Group ID : 0


Remote VC Label : 0

Local VC MTU : 4470

Remote VC MTU : 0

Local VCCV : Disable Remote VCCV : None Local Frag : Disable Remote Frag : None Local Ctrl Word : Enable Remote Ctrl Word : None Tunnel Policy : --




# Another interface on PE also has a VC with the ID as 100, whose link layer protocol is HDLC.

[PE-Pos4/1/0] display mpls l2vc interface pos 4/1/0 *Client Interface : Pos4/1/0 is down Session State : down AC State : down




Issue 01 (2008-08-20)

VC State : down VC ID : 100 VC Type : hdlc Destination : 2.2.2.8

Local Group ID : 0

Remote Group ID : 0


Remote VC Label : 0

Local VC MTU : 4470

Remote VC MTU : 0

Local VCCV : Disable Remote VCCV : None Local Frag : Disable Remote Frag : None Local Ctrl Word : Disable Remote Ctrl Word : None Tunnel Policy : --




# Change the link layer protocol of POS 4/0/0 to HDLC.

[PE-Pos4/0/0] link-protocol hdlc

# Recheck POS 4/0/0 and find that no VC is existing.

[PE-Pos4/0/0] display mpls l2vc interface pos 4/0/0

# Check PE and find that only one VC is left. This VC is on POS 4/1/0 whose link layer protocol is HDLC.

[PE] display mpls l2vc Total ldp vc : 1 0 up 1 down *Client Interface : Pos4/1/0 Session State : down AC Status : down VC State : down VC ID : 100 VC Type : hdlc Destination : 2.2.2.8


Remote VC Label : 0


Remote VC MTU : 0




Create time : 0 days, 0 hours, 8 minutes, 26 seconds UP time : 0 days, 0 hours, 0 minutes, 0 seconds Last change time : 0 days, 0 hours, 8 minutes, 26 seconds



4-29

Fault Analysis When an interface (POS 4/1/0 for example) on PE has an HDLC-type PW with the ID of 1, and you change the link layer protocol of another interface (POS 4/0/0 for example) to HDLC, the system will delete the PW under POS 4/0/0 automatically. The reason is that the two PWs have the same VC ID and the same VC type.

Troubleshooting Procedure Step 1 If you need to change the link layer protocol of a VC, ensure that no identical PW ID and VC

type are configured on other interfaces of the same router.

----End

Summary The combination of VC ID and VC type must be unique on the same router.

If a VC changes its link protocol type and this causes a conflict with the other VCs, the VC will be automatically deleted.

4.3.7 Both the Session and the AC Are Up, But the VC Cannot Be Up

Fault Symptom


CE1 CE2

PE1 PE2

Ethernet1/0/010.1.1.1/24

Ethernet1/0/010.1.1.2/24

Ethernet1/0/010.1.1.1/24

GE1/0/010.1.1.2/24

Ethernet2/0/0100.1.1.2/24

Ethernet2/0/0100.1.1.1/24

As shown in Figure 4-16, the VC is not Up after Martini MPLS L2VPN is configured. Check the session and the AC, and find both of them are Up.

Fault Analysis Use the display mpls l2vc vc-id command on PE to check the MTU value for consistency. For example:

# Check the MTU value of the Ethernet interface on PE1.

[PE1-Ethernet1/0/0] display mpls l2vc 100 Total ldp vc : 1 0 up 1 down *Client Interface : Ethernet1/0/0




Issue 01 (2008-08-20)

Session State : up AC Status : up VC State : down VC ID : 100 VC Type : ethernet Destination : 2.2.2.2 Local VC Label : 119808

Remote VC Label : 25600 Control Word : Disable Local VC MTU : 80

Remote VC MTU : 120





# View the MTU value of the Ethernet interface on PE2.

[PE2-Ethernet1/0/0] display mpls l2vc 100 Total ldp vc : 1 0 up 1 down *Client Interface : Ethernet1/0/0 Session State : up AC Status : up VC State : down VC ID : 100 VC Type : ethernet Destination : 1.1.1.1 Local VC Label : 25600

Remote VC Label : 119808


Remote VC MTU : 80





The display shows that the MTU value of the local end is not consistent with that of the remote end, which leads to parameter negotiation failure.

Modify the interface MTU value on either PE to make the MTU value consistent at both ends.

For example, change the MTU value of the interface on PE2 to make it consistent with that on PE1.

[PE2-Ethernet1/0/0] mtu 80 [PE2-Ethernet1/0/0] shutdown [PE2-Ethernet1/0/0] undo shutdown

After modification, the VC becomes Up.

[PE2-Ethernet1/0/0] display mpls l2vc 100 Total ldp vc : 1 1 up 0 down *Client Interface : Ethernet1/0/0



4-31

Session State : up AC Status : up VC State : up VC ID : 100 VC Type : ethernet Destination : 1.1.1.1 Local VC Label : 25600



Remote VC MTU : 80





Troubleshooting Procedure Step 1 Check that the MTU value is consistent at both ends.

Step 2 If inconsistency occurs, modify the MTU value on either end to ensure consistency.

Step 3 Use the shutdown command and then the undo shutdown command on the modified interface.

----End

Summary PWE3 has extended Martini interface parameters. Some of them must be supported, and some of them need not be supported. Some of them must be matched while some of them need not match during the negotiation.

The following lists the Martini interface parameters.

Code Length Description

0x01 4 Interface MTU in octets

0x02 4 Maximum Number of concatenated ATM cells

0x03 up to 82 Optional Interface Description string

0x04 4 CEM [8] Payload Bytes

0x05 4 CEM options

The following shows the PWE3 interface parameters.


0x01 4 Interface MTU in octets




Issue 01 (2008-08-20)


0x02 4 Maximum Number of concatenated ATM cells

0x03 Up to 82 Optional Interface Description string

0x04 4 CEP/TDM Payload Bytes

0x05 4 CEP options

0x06 4 Requested VLAN ID

0x07 6 CEP/TDM bit-rate

0x08 4 Frame-Relay DLCI Length

0x09 4 Fragmentation indicator

0x0A 4 FCS retention indicator

0x0B 4/8/12 TDM options

0x0C 4 Virtual Circuit Connectivity Verification (VCCV) parameter

Items from 0x06 to 0x0C are extended in PWE3.

Currently, the VRP5.30 supports the MTU, Maximum ATM cell number, Fragmentation and VCCV, but does not support the Request VLAN ID. You can set the same VLAN ID for the AC interface at both ends to rectify the problem of not supporting the Request VLAN ID.

When configuring interface parameters, note the following:

The same MTU must be specified for the Ethernet-type interface; otherwise, the PW cannot be Up.

In ATM cell (0x0003 ATM transparent cell transport, 0x0009 ATM n-to-one VCC cell transport and 0x000A ATM n-to-one VPC cell transport) mode, the maximum ATM cell number must be sent to the peer in order to inform the peer how many cells it can handle at a time. When the remote end encapsulates packets, this number should not increase. Inconsistency of the cell number at both ends does not affect the status of a PW.

Fragmentation and ATM cell handling mode are consistent at both ends. The configuration of fragmentation and ATM cell handling mode is optional. The local end only informs the remote whether it can perform reassembly; whether the remote fragments packets depends on the packet size and its fragmentation capability. The fragmentation capability does not affect the status of a PW, and it is not necessary to be the same.

VCCV processing is similar to ATM cell and fragmentation capability in terms of function. The VCCV configuration is optional. It is used to inform the remote of its VCCV capability. When performing VCCV, the peer chooses a path (CC) and a method (CV) according to the configuration at both ends. VCCV does not affect the status of a PW, and is not required consistent at both ends.

The Request VLAN ID is used to inform the peer of its capability. During the forwarding, the remote is required to push a VLAN ID on its Layer 2 frame header. Other means can also be used. This configuration is optional. If the Request VLAN ID is chosen, the VLAN ID can be different at both ends.



4-33

4.3.8 Ethernet Interconnects with ATM, the VC Is Up, But the Ping Between CEs Fails

Scenario


Backbone

CE1 CE2

PE1 PE2

GE1/0/0

GE1/0/0 ATM1/0/0

ATM1/0/0

As shown in Figure 4-17, Ethernet interconnects ATM. After L2VPN IP-interworking is configured, the VC at both ends is Up, but the ping between CEs fails.

Fault Analysis Check whether the IP address of the two CEs is on the same network segment. The address of the two ends must be on the same network segment.

Use the display local-ce mac command on PE, and use the display arp command on CE to check the establishment of ARP entries of the Ethernet link.

If ARP entries are not set up successfully, configure the IP address and the MAC address for the Ethernet interface of CE on PE and also enable MAC broadcasting on it. That is, run the local-ce ip command, the local-ce mac command and the local-ce mac broadcast command on PE.

For detailed configuration, refer to the L2VPN IP-interworking configuration described in Chapter 6 "MPLS L2VPN Configuration" in the VRP Configuration Guide - VPN.

The IP address configured on PE is that of the corresponding interface on remote CE.

For ARP entries of the ATM link, you can use one of the two methods:

Use INARP to generate MAP dynamically. Figure 4-18 shows an example to configure IP addresses. The configuration is as follows. [PE2] interface atm1/0/0 [PE2-Atm1/0/0] pvc 100/200 [PE2-atm-pvc-Atm1/0/0-100/200] map ip inarp broadcast [PE2-atm-pvc-Atm1/0/0-100/200] ip address 10.1.1.1 255.255.255.0 [CE2] interface atm1/0/0 [CE2-Atm1/0/0] pvc 100/200 [CE2-atm-pvc-Atm1/0/0-100/200] map ip inarp broadcast [CE2-atm-pvc-Atm1/0/0-100/200] ip address 10.1.1.2 255.255.255.0




Issue 01 (2008-08-20)

Figure 4-18 IP address configuration diagram

Backbone

CE1 CE2

PE1 PE2

GE1/0/010.1.1.1/24

GE1/0/010.1.1.2/24

ATM1/0/010.1.1.1/24

ATM1/0/010.1.1.2/24

Use static MAP. Configure the map ip peer-ce-address broadcast command or the map ip default broadcast command in the PVC view of the ATM interface at both ends of the AC. For example:

[PE2] interface atm1/0/0

[PE2-Atm1/0/0] pvc 100/200 [PE2-atm-pvc-Atm1/0/0-100/200] map ip 10.1.1.2 broadcast [PE2-atm-pvc-Atm1/0/0-100/200] ip address 10.1.1.1 255.255.255.0 [CE2] interface atm1/0/0 [CE2-Atm1/0/0] pvc 100/200 [CE2-atm-pvc-Atm1/0/0-100/200] map ip 10.1.1.1 broadcast [CE2-atm-pvc-Atm1/0/0-100/200] ip address 10.1.1.2 255.255.255.0

Troubleshooting Procedure Step 1 Check that the IP address of CE at both ends is on the same network segment.

Step 2 Run the display local-ce mac command on PE and run the display arp command on CE to check whether ARP entries of the Ethernet link are set up successfully.

Step 3 If ARP entries are not set up successfully, configure an IP address and MAC address for the AC interface of Ethernet type and enable MAC broadcasting on PE. For the ATM link, use INARP to generate MAP dynamically or use static MAP.

----End

Summary In IP-interworking applications, if the VC is Up but the ping between CEs fails, the cause is often configuration error.

You should perform configuration according to the link type, so that ARP entries can be generated correctly.



4-35

4.3.9 CEs Cannot Communicate by Using the Accessing Mode of VLAN

Fault Symptom CEs adopt the accessing mode of VLAN. After the VLAN ID is changed, CEs on two ends cannot communicate.

Fault Analysis To modify the VLAN ID, you need to modify VC IDs of the AC interfaces along the packet-sending direction in turn. To make sure the modification takes effect, run the shutdown command and then the undo shutdown command on each VLAN interface.

Troubleshooting Procedure Step 1 Use the vlan-type command on the AC interfaces along CE to PE and PE to CE direction to

modify the VLAN ID.

Step 2 Use the shutdown command on the AC interfaces to disable the interfaces.

Step 3 Use the undo shutdown command on the interfaces to enable them.

----End

Summary When the VLAN access is adopted between CE and PE, the minimum VLAN ID of interfaces on both ends of the AC that the packet passes by must be consistent. Otherwise, the packet cannot be forwarded normally.

The minimum VLAN IDs of the CE interfaces on both ends of the tunnel can be different.

4.3.10 CEs Cannot Access Each Other Though the Static VC Is Up

Fault Symptom After the static VC is configured, the static VC is Up. CEs, however, cannot access each other.

For example:

[PE1] display mpls static-l2vc

Total svc connections: 1, 1 up, 0 down

*Client Interface : Ethernet2/0/1 is up

AC Status : up

VC State : up

VC ID : 0

VC Type : ethernet

Destination : 2.2.2.2

Transmit VC Label : 200

Receive VC Label : 100

Control Word : Disable

VCCV Capability : Disable




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Create time : 0 days, 0 hours, 0 minutes, 17 seconds

UP time : 0 days, 0 hours, 0 minutes, 17 seconds

Last change time : 0 days, 0 hours, 0 minutes, 17 seconds

Fault Analysis Check the label of the static VC on the PE of the opposite end:

[PE2] display mpls static-l2vc

Total svc connections: 1, 1 up, 0 down

*Client Interface : Ethernet1/0/1 is up

AC Status : up

VC State : up

VC ID : 0

VC Type : ethernet


Transmit VC Label : 200

Receive VC Label : 100


VCCV Capability : Disable







You can see that the label configuration on the local PE is different from that of the peer.

CEs can communicate after the following configuration.

[PE1-Ethernet2/0/1] mpls static-l2vc destination 2.2.2.2 transmit-vpn-label 100


Troubleshooting Procedure Step 1 Delete the static VC on one end and reconfigure it.

----End

Summary When the label of the static VC is incorrect, the data cannot be forwarded normally even though the VC is Up.

When configuring the static VC, note the following:

The local transmit-vpn-label and the remote receive-vpn-label are consistent. The local receive-vpn-label and the remote transmit-vpn-label are consistent.



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4.3.11 VC Is Down Though AC Is Up

Fault Symptom After the configuration of L2VC, the AC is Up. However, the ping of the peer fails. After using the display mpls l2vc command, you will find the status of the VC is Down and all the remote VC label and the remote VC MTU are zeros, which are invalid.

[PE] display mpls l2vc

Total ldp vc : 1 0 up 1 down

*Client Interface : Atm5/0/0

Session State : up

AC Status : up

VC State : down

VC ID : 100

VC Type : ppp



Remote VC Label : 0


Local VC MTU : 1500

Remote VC MTU : 0







Fault Analysis Possible causes are:

The encapsulation types on two ends are different. The peer is not configured with VC.

Troubleshooting Procedure Step 1 Check that the correct peer addresses are configured on PEs of two ends.

Step 2 Check that the VC IDs on two ends are consistent.

Step 3 Check that the encapsulation types on two ends are consistent.

Step 4 Check that the local VC MTU and the remote VC MTU are consistent.

Step 5 Check that the control word is enabled or disabled on both ends.

----End

Summary VC adopts LDP as the signaling. The negotiation of following parameters is required:

VC type




Issue 01 (2008-08-20)

Control word MTU

Thus, the VC status can be Up only when those parameters are consistent on both ends.

4.3.12 Large-Sized Packets Are Lost Between CEs on Two Ends of L2VPN

Fault Symptom After the L2VPN is set up between CEs, some large-sized packets are lost.

Fault Analysis The cause may be due to the fragmentation of the large-sized packets. The fragmentation may have been caused by the MTU on the AC interfaces or the receiving interface is smaller than the MTU of the source interface.

Troubleshooting Procedure Step 1 Use the display interface command on the source interface to check the MTU.

Step 2 Use the display interface command on the PEs that the packet passes by to check whether there are AC interfaces whose MTU is smaller than the MTU of the source interface.

Step 3 Use the mtu command in the AC interface view on CE or PE to increase the MTU value and thus ensure the packet sent by CE is not fragmented.

----End

Summary When CEs are connected through the L2VPN, the sent packet passing through PEs cannot be fragmented. Otherwise, the packet cannot be received normally.



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4.3.13 Fail to Establish the MPLS LDP Session Between PEs When RIP-1 Are Used in the L2VPN Backbone

Fault Symptom

Figure 4-19 Networking diagram of the L2VPN backbone adopting RIP

PE-B

CE-A CE-B

Loopback01.1.1.1/32

POS2/0/0100.1.1.2/24

POS2/0/0100.1.1.1/24

POS1/0/010.1.1.1/24

POS1/0/0 POS1/0/0

POS1/0/010.1.1.2/24

Loopback02.2.2.2/32

PE-A P

POS3/0/01.1.2.3/16

POS3/0/01.1.2.4/16

After the L2VPN backbone network running RIP-1 advertises the local loopback0 address and the interface IP address, the MPLS LDP session between PEs cannot be set up.

The prompt on PE-A is as follows:

Del Session : EncdecEncode ldp notify msg failure.

Check the MPLS LDP session on PE-A. The display is as follows:

[PE-A] display mpls ldp session

LDP Session(s) in Public Network

--------------------------------------------------------------------------

Peer-ID Status LAM SsnRole SsnAge KA-Sent/Rcv

-------------------------------------------------------------------------

2.2.2.2:0 NonExistent Passive 0/0

-------------------------------------------------------------------------

LAM : Label Advertisement Mode SsnAge Unit : DDD:HH:MM

The prompt on PE-B is as follows:

Del Session : Tcp connection down

Check the MPLS LDP session on PE-B. The display is as follows:

[PE-A] display mpls ldp session

LDP Session(s) in Public Network

--------------------------------------------------------------------------

Peer-ID Status LAM SsnRole SsnAge KA-Sent/Rcv

-------------------------------------------------------------------------

1.1.1.1:0 Initialized Active 0/0

-------------------------------------------------------------------------

LAM : Label Advertisement Mode SsnAge Unit : DDD:HH:MM




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Fault Analysis Check the routing table on PE-B. The display is as follows:

[PE-B] display ip routing-table

Routing Tables: Public

Destinations : 10 Routes : 10

Destination/Mask Proto Pre Cost NextHop Interface

1.0.0.0/8 RIP 100 1 100.1.1.1 Pos2/0/0

1.1.0.0/16 Direct 0 0 1.1.2.3 Pos3/0/0

1.1.2.3/32 Direct 0 0 127.0.0.1 InLoopBack0

1.1.2.4/32 Direct 0 0 1.1.2.4 Pos3/0/0


100.1.1.0/24 Direct 0 0 100.1.1.2 Pos2/0/0

100.1.1.1/32 Direct 0 0 100.1.1.1 Pos2/0/0




RIP-1 can identify only the route of the natural segment such as class A, B and C.

In the routing table of PE-B, there are two routes to peer 1.1.1.1.

The IP address 1.0.0.0/8 learned by RIP-1. The IP address 1.1.0.0/16 directly connected with PE-B.

According to the longest matching rule, the packet is sent to POS 3/0/0 whose IP address is 1.1.0.0/16. In the network segment connected with POS 3/0/0, the loopback address 1.1.1.1/32 does not exist. Therefore, the MPLS LDP session cannot be set up.

Troubleshooting Procedure Step 1 Replace RIP-1 with RIP-2 to advertise the 32-bit loopback address. This address serves as the

MPLS LDP session address, on the PE.

----End

Summary RIP-1 can identify only the route of the natural segment such as class A, B and C. Therefore, RIP-2 should be adopted to advertise the 32-bit loopback address of PE.

4.4 FAQs

Q: How Can I Run Martini Mode on the Existent Version? A: The VRP5.30 defaults to run PWE3 and also supports compatibility with Martini mode. If it is required to work only in Martini mode, use the mpls l2vpn default martini command in the system view.

You can use the undo mpls l2vpn default martini command to restore PWE3 mode.



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If a VC has been configured, such a type of switching cannot be done.

Q: In What Cases Do I Configure local-ce and local-mac in Different Media Interworking?

A: You need to configure the local-ce and local-mac when setting IP-interworking encapsulation on an L2VPN Ethernet interface or sub-interface on PE. After an L2VPN Ethernet interface is IP-interworking encapsulated, it learns MAC addresses in a new way. Accordingly, its ARP entries are different from ordinary ARP entries.

When PE receives an ARP request from CE through an IP-interworking encapsulated L2VPN ingress interface, PE responds with its own MAC address regardless of the destination. At this time, an Ethernet interface or sub-interface of PE can connect only one CE, but cannot connect multiple CEs through a Hub or LAN switch. When an Ethernet interface or sub-interface of PE connects multiple CEs, PE may learn unhelpful MAC addresses, which may cause forwarding failure.

Q: What Special Configuration Should Be Done on an FR Interface? What Is the Configuration Guideline When CE Acts as DCE and PE Functions as DTE?

A: When you configure FR, note that:

You must configure a VC ID for a DCE or NNI interface regardless of whether it is a main interface or a sub-interface.

For a DTE interface, if it is a main interface, the system automatically determines its VC ID based on the remote device; if it is a sub-interface, you must manually specify a VC ID for it.

When CE adopts FR to access PE, there is no special requirement on the interface connected with CE on the PE.

In the two CEs setting up the connection, the interface connected with PE on one CE is specified as DCE while that of another CE is specified as DTE.

Refer to Figure 4-20.

Figure 4-20 Networking scheme using DCE and DTE as the interface types

VPNBackbone

DCE DTE

PE2PE1

CE2CE1

When configuring LSP, configure link mapping to permit the broadcast packets if PEs are connected through NBMA network such as FR, ATM, and X.25.




Issue 01 (2008-08-20)

Q: What Is the Function of the Control Word in L2VPN? A: The control word on the PWE3 control plane is represented by a bit. The VC can be Up only when the control word at both ends is the same.

If the forwarding plane supports the control word, a 32-bit field is added to the data packet to show the packet order. Generally, disorder may occur in the case of load balancing.

When PEs are connected through the Ethernet, and PE and CE are connected in a PPP fashion, PPP negotiation will fail because the control packet of PPP is too small, less than the minimum MTU supported by the Ethernet. In this case, the control word is used as padding to avoid this problem.

Q: Can I Specify Multi-Hop VCs with the Same Peer and Different Encapsulation Types When Configuring Switch-L2VC on SPE?

A: Yes, you can. A VC is determined by the combination of the VC ID and the VC type.

Q: Can I Set the PW ID to Zero or Ignore Its Configuration? A: Yes, you can. You can set a PW ID for a static PW or choose not to set it. A static PW with a PW ID of Zero cannot switch with other PWs.

Q: How Can I Configure L2VPN Load Balancing? A: Load balancing is to use multiple tunnels to carry a PW. Data payload is divided among these tunnels and forwarded by them. The number of load balancing tunnels is determined by the permit file.

When configuring load balancing, you need to specify a tunnel selection policy, that is, specify a policy name when configuring VCs.

Q: What Are the Conditions for a PW Being Up? A: In a SVC, if a PW is to be Up the conditions are: the local AC is Up and the tunnel is Up. You can use the display mpls static-l2vc interface command to check the PW status.

In LDP, the conditions for a PW being Up are:

The local AC is Up. The tunnel is Up. The LDP session is Up. The MTUs, VC types and control words are consistent on both ends.

You can use the display mpls l2vc interface command to check the PW status.

Q: What Are the Differences Between Tag or Untagged Configuration in the Ethernet Interface View and Tagged or Raw Configuration in the PWE3 View?

A: The tag or untagged mode of an Ethernet interface has no direct relation with the tagged or raw mode of a PWE3 tunnel.

The tag or untagged mode of an Ethernet interface is used to identify a VLAN and a sub-interface that will receive packets sent from AC. By default, Ethernet packets are untagged and VLAN packets are tagged.



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The tagged or raw mode of PWE3 is used to set the PWE3 payload to carry a VLAN tag. A PWE3 packet coming out of a tunnel finds its egress based on the tagged or raw configuration.

The fact that the PWE3 packet carries the VLAN tag does not imply that the Ethernet interface bound with the PWE3 tunnel is configured with the VLAN tag.

Specifying the PWE3 with the Raw mode, you can realize the switching function of the VLAN tag. For example, the local AC interface is the Ethernet main interface while the remote is the Ethernet sub-interface:

The packet is received on the Ethernet main interface and the packet is untagged. The VLAN tag is not added to the packet because the mode of PWE3 is Raw. When the PWE3 tunnel sends the packet to the remote end, the VLAN tag is added to the packet because the egress is an Ethernet sub-interface.

After the remote Ethernet sub-interface receives the packet with the VLAN tag, according to the Raw mode, the interface removes the VLAN tag and sends out the packet from the Ethernet main interface.

If both ends of a PW are a VLAN sub-interface in tag mode, the same VLAN tag must be set for them. Otherwise, the packet is discarded.

In Q-in-Q mode, packets entering a tunnel carry multiple layers of tags. If the mode of PW is Raw, packets will be removed one layer of outer tag before being forwarded to the remote tunnel with the inner label.

For a VLANIF interface, the VLAN packet does not carry a VLAN tag by default. If PWE3 is configured in tag mode, the forwarding engine will add a default VLAN tag to packets. The main Ethernet interface can emulate the default VLAN and make packets be in default VLAN mode.

Therefore, when configuring PWE3 on the interface of Ethernet type, you can configure the packet to be tagged or untagged manually instead of judging from the interface type.

Q: After CEs Adopt the ATM to Access PEs, All the CE Interfaces and PE Interfaces Are Up. Why Cannot the CEs on Two Ends Ping Through Each Other?

A: Check and ensure PVC of the interface connected with CE on the PE, and that of the interface connected with PE on the CE are consistent.

Q: If an Interface Is Bound to L2VPN and L3VPN Concurrently, Which Configuration Takes Effect, L2VPN or L3VPN?

A: An interface cannot serve as the L2VPN AC interface and the L3VPN AC interface at the same time. After an interface is bound to L2VPN, the Layer3 features such as IP addresses and routing protocols configured on this interface become invalid. If an interface is bound to L2VPN and L3VPN at the same time, only the L2VPN configuration takes effect. After the L2VPN configuration is deleted, the bound L3VPN configuration becomes available.




Issue 01 (2008-08-20)

4.5 Diagnostic Tools 4.5.1 display Commands

Command Description

display mpls l2vc Displays information on L2VC.

display tunnel-info Displays information on tunnels.

display mpls lsp Displays information on LSPs.

display mpls ldp Displays information on LDP.

display mpls l2vpn connection Displays information about the L2VPN using BGP as the signaling.

display mpls l2vpn Displays the MPLS L2VPN information.

display mpls l2vc # View information on the bound L2VC of a specified interface.

<Quidway> display mpls l2vc interface ethernet1/0/0 *Client Interface : Ethernet1/0/0 is up Session State : up AC State : up VC State : up VC ID : 10

VC Type : ethernet Destination : 2.2.2.2

Local Group ID : 0

Remote Group ID : 0



Local VC MTU : 1500

Remote VC MTU : 1500

Local VCCV : Disable Remote VCCV : Disable Local Frag : Disable Remote Frag : Disable Local Ctrl Word : Disable Remote Ctrl Word : Disable Tunnel Policy : --



VC tunnel/token info : 1 tunnels/tokens NO.0 TNL Type : lsp , TNL ID : 0x1002000 Create time : 0 days, 0 hours, 2 minutes, 13 seconds UP time : 0 days, 0 hours, 0 minutes, 39 seconds Last change time : 0 days, 0 hours, 0 minutes, 39 seconds



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display tunnel-info # View information on all tunnels.

<Quidway> display tunnel-info all * -> Allocated VC Token Tunnel ID Type Destination Token ----------------------------------------------------------------------

0x1002000 lsp 2.2.2.2 0 0x51002001 local ifnet -- 1

4.5.2 debugging Commands

Command Description

debugging mpls l2vpn Debugs L2VPN.

debugging mpls packet Debugs MPLS packets.

Documents

01-04 MPLS L2VPN Troubleshooting